Heterodyne receiver



km. 31, 19 3 9. J..L. H. JONKER ET AL W fi HETERODYNE RECEIVER Filed Sept'. 29, 1936 2 Sheets-Sheet l 8 0XIDE 1 COATING C MM-0% pi OXIDE 7 COATING INVENTORS ATTORN EY Jam. 31, 1939.- J. L. H. JONKER ET AL v 9 HE'I'ERODYNE RECEIVER Filed-Se t. 29, 1936 2 Sheets-Sheet 2 [Mrs SECOND I. 4 y 3- Arm saw-Row ISM/T5 550mm ma mama Mme/1150mm ppm/mar wil ' Mum/[0mm FR'OUE/VCX INVENTORS JHIIIHIII llhhhl-mlnlmH ATTORNEY J- L Jr. JON/(ER AgM/V. VAN UVERBEEK Mm Patented Jan. 31, 1939 UNITED STATES PATENT OFFICE HETERODYNE RECEIVER Philips Gloeilampenfabrieken,

Eindhoven,

Netherlands, a corporation of the Netherlands Application September 29, 1936, Serial No. 103,094 In the Netherlands October 4, 1935 4 Claims.

This invention has reference to an electric discharge tube and to a heterodyne circuit comprising such a tube.

In the use of electric discharge tubes, particularly tubes for amplifying electric oscillations, it is often desirable that the slope of the anode current-grid voltage characteristic or the mutual conductance should be a maximum. Wherever hereinafter reference is made to mutual conductance of the tube it is to be understood to mean the steepness of the characteristic just mentioned.

Various means permitting of attaining the object here mentioned have been described; these 3 means essentially consist of choosing given pro portions in designing the various electrodes by means or which the characteristic of the tube, including also the mutual conductance, can be regulated in some measure.

According to the invention, a construction is devised by means of which a substantial increase in mutual conductance of the tube can be obtained and in which not so much the dimensions of the electrodes as the properties of the surface of given electrodes are used as a starting point.

-ccording to the invention, for this purpose an electric discharge tube comprising an electrode system including an apertured anode is provided, and on the side of this anode remote from the cathode, there is provided an electrode the surface of which has such properties that when the tube is in use secondary electrons are evolved from it. For this purpose the surface of this electrode is, preferably, coated with a substance readily emitting electrons, such for example as Preferably, this separate electrode has applied to it a positive voltage which is generally lower than the voltage of the anode; for this purpose this electrode may, for example, be connected to the screening grid.

Although generally the electrode that emits secondary electrons is arranged directly behind the anode it is also possible to arrange between this electrode and the anode a regulating grid permitting of regulating the number of secondary electrons reaching the anode. The latter condition is particularly advantageous when, according to a particular embodiment of the present invention, a discharge tube of the kind here described is used as a mixing tube in a circuit. In this case, the secondary emission electrode may serve jointly with the said regulating grid for generating the local oscillations. It is also possible to use as a mixing tube a discharge tube according to the present invention without regulating grid and in this case the secondary emission electrode between which electrode and the oathode a negative resistance occurs can serve alone as a local oscillator. A discharge tube according to the present invention is not only adapted for use as a mixing tube but in many other circuit arrangements, for example, as an amplifier.

In order that the invention may be clearly understood and readily carried into effect it will now be described more fully by way of example with reference to the accompanying drawings in which:

Figs. 1 and 2 show respectively a front view in perspective and a plan view of a discharge tube according to the present invention, the tube envelope in each case being partially removed to show the electrode arrangement.

Fig. 3 discloses an amplifying circuit utilizing the discharge tube shown in Figs. 1 and 2.

Fig. 4 discloses a mixing or heterodyne circuit utilizing the same tube, and

Fig. 5 discloses a mixing or heterodyne circuit utilizing a modified form of tube.

Referring to the drawings, I designates the wall of the tube which is provided at the bottom with a base 2 comprising connecting members 3. Internally oi the tube is arranged an electrode system comprising a cathode 4, in the present case an indirectly heated cathode, a control grid 5, a screening grid 6, a wire-shaped anode 1 and an electrode 8 emitting secondary electrons. The various electrodes are supported at the top and maintained at the correct relative spacing by a mica plate 9. All the electrodes are connected to current supply members which are taken out through the press (not shown) except for the leading-in wire for the control grid which is taken through the top of the bulb at H).

Figure 3 shows an amplifier circuit in which a discharge tube according to the invention is used. In this circuit the oscillations to be amplified are supplied to the grid 5 and the amplified oscillations occur between the anode 1 and the cathode. Owing to the fact that the tube has arranged in it an electrode 8 which has a positive voltage relatively to the-cathode and emits secondary electrons material amplification is obtained.

Fig. 4 shows a circuit arrangement in which a discharge tube according to the invention is used as a mixing tube and Fig. 5 shows a circuit arrangement of. this kind in which a regulating grid H is interposed between the anode and the secondary emission electrode. In the two lastmentioned figures, the arrangement comprises an input circuit l2 which is connected between the cathode 4 and the first or signal control grid 5, an oscillatory circuit l3 which is connected between the secondary emission plate electrode 8 and an intermediate point of the high potential source, and the load or output circuit M which is tuned to the difference or intermediate frequency connected between the perforate output electrode 7 and the high potential source. The circuit of Fig. 5 differs from that of Fig. 4 in that an auxiliary electrode II which serves to control the secondary emission from plate 8 has connected to it a coil l5 which is inductively coupled to :the coil of the oscillatory circuit I 3. The electrodes II and 8 are shown connected to the same source of dc potential.

Although only a few embodiments of the pres ent invention are illustrated, it is evident that a plurality of constructions of a discharge tube .or a heterodyne circuit embodying the invention are possible.

Having described our invention, what we claim as novel and desire to secure by Letters Patent is:

1. In a radio receiver, the combination of an electron discharge tube having a cathode, a signal control grid, an apertured anode, a second grid and a fifth electrode arranged in the order named, said fifth electrode: having its interior surface formed of a material which readily emits electrons, a circuit tuned to a desired signal frequency connected between said signal control grid and cathode, an output circuit tuned to the intermediate frequency connected to said apertured anode, a parallel resonant circuit tuned to a local oscillation frequency connected to said fifth electrode and cathode, and a circuit connected to said second grid and including a feedback connection to said last named resonant circuit.

2. In a radio receiver, the combination of an electron discharge tube having a cathode, a signal control grid, ananode formed vof spaced apart turns, a second grid and a fifth electrode arranged in the order named, said fifth electrode having its interior surface formed of electron emitting material, a circuit adjustably resonant to a desired signal frequency connected between said signal control grid and cathode, an output circuit tuned to the intermediate frequency connected to said anode, a parallel resonant circuit including a coil tuned to a local oscillation frequency connected to said fifth electrode and a circuit connected to said second grid and including a coil inductively coupled to the coil of said parallel resonant circuit.

3. The combination with an electron discharge device provided with a cathode, a plate electrode and three interposed perforate electrodes, the one next adjacent the plate electrode being an output electrode, said plate electrode having on its inner surface an oxide coating which is capable of. emitting secondary electrons as a result of primary electron impact, of an input circuit connected between cathode and the perforate electrode next adjacent thereto, an output circuit including a source of positive potential connected between cathode and the perforate output electrode, and means for impressing on both the intermediate perforate electrode and the emissive plate electrode a positive potential lower than that on the perforate output electrode.

4. The combination with an electron discharge device provided with a cathode, a plate electrode and a plurality of interposed perforate electrodes, an intermediate one of which is an output electrode, said plate electrode being capable of emitting secondary electrons as a result of primary electron impact, of an input circuit includ- ,ing a tunable circuit resonant to a signal frequency connected between cathode and the perforate electrode next adjacent thereto, an output circuit including a source of positive potential and a tunable circuit resonant to an intermediate frequency connected between cathode and the perforate output electrode, and circuit elements connected between the emissive plate electrode and the perforate electrode next adjacent thereto for generating local oscillations of a frequency which combines with the oscillations of signal frequency to produce the oscillations of intermediate frequency in the output circuit.

J OHAN LODEWIJK HENDRIK J ONKER. ADRIANUS J OHANNES W'ILHELMUS MARIE VAN OVERBEEK. 

